1. Field of the Invention
The present invention relates to radiant heating and cooling systems, and, more specifically, to modular panel radiant heating systems for heating a room by either circulating a liquid through tubing, or applying voltage to electrical heating cables contained in heat transfer panels secured to the rear side of floor, wall, or ceiling surfaces. Room cooling may, with some restrictions, also be accomplished by circulating a chilled liquid through tubing in the panels.
2. Discussion of Related Art
Radiant systems for room heating have been in use for nearly 80 years. Many such systems circulate hot water through metal or plastic tubing embedded in concrete or plaster surface materials. However, plaster is now less frequently used, and concrete floors are less popular than raised wcod-framed floors in many climate areas with substantial heating loads. With raised wood-framed floors, radiant heating is presently at a disadvantage compared to forced-air heating systems when considering the cost of a concrete floor topping to surround the tubes. Also, radiant heating systems are expensive to retrofit to existing buildings because adding the weight and thickness of a concrete topping can require costly alterations such as strengthening the floor structure, shortening doors, and moving baseboards. Electric radiant heating systems have usually been placed in ceilings, and have lost popularity due to high operating costs.
One attractive option for reducing the cost of new and retrofit hydronic radiant heating systems for use with wood-framed floor, wall, and ceiling assemblies is to secure lightweight tubing or hydronic panel assemblies in thermal contact with the rear sides of surface panel materials supported by the wood framing members. Various concepts and apparatus for such systems may be found in the prior art. A rubber "tubemat" product is produced and comprises multiple small tubes joined in a flat panel which may be stapled or otherwise secured to a surface. However, this configuration is expensive, fails to provide adequate lateral heat-spreading from the tubes, cannot easily provide reliable contact with the room surface, and requires additional labor for placing insulation to limit heat losses from the rear side of the tubemat.
An early prefabricated modular panel is shown in U.S. Pat. No. 2,548,036 comprising a double metal sheet with integral serpentine tubing pattern and surface deformations to improve bonding to a plaster surface. European Patent WO 82/01058 shows a lightweight assembly more appropriate for installation against current "dry" surface panels; the assembly comprises a metal surface sheet with grooves holding heat exchange tubes placed parallel to the wood supporting frame and a foam insulation backing. The semi-flexible assembly is arched to maintain contact with the back surface after installation. The metal sheet is designed to spread heat laterally from the tubes and extends between wood framing and surface panel to secure the assembly in place. However, this fastening configuration prevents installation after placement of the interior surface material.
Other designs in the prior art provide modular panel assemblies including water passages, a metal heat-spreading surface, and plastic or other insulation backing from which the assemblies derive their rigidity. However, the prior art systems do not include components facilitating rapid installation in retrofit applications, nor do they provide fastening systems which are likely to maintain positive contact with the room surface over a long period of time. The prior art systems do not provide panel designs with rigid insulation shaped to maximize thermal and structural performance of the insulation material. Prior art systems also fail to maximize heat transfer in locations where surface irregularities prevent contact.